The present invention relates generally to a magnetic transfer apparatus for writing a servo signal to a magnetic recording medium by a magnetic transfer technology, and an optical inspection apparatus for inspecting a condition of a surface of the magnetic recording medium, which are particularly featured in greasing agent used in these apparatus. More particularly, the invention relates to a magnetic transfer apparatus, which is featured by a greasing agent used in the apparatus, for writing a positioning servo signal for a data writing/reading head written on a surface of a magnetic recording medium to a magnetic recording medium by a magnetic transfer technology in a hard disk drive employing a magnetic film as a storage material as a currently major trend as external storage device of computers, and an optical inspection apparatus, which is featured by a greasing agent used in the apparatus, for inspecting scratch on the surface of a magnetic recording medium and contaminating condition of before and after magnetic transfer. Also, the present invention relates to a magnetic recording medium to be produced by the magnetic transfer apparatus.
In a hard disk drive used as an external storage device of a personal computer, a magnetic head is floated above a surface of a rotating magnetic recording medium by means of a floating mechanism called as slider with maintaining a distance of several tens nanometer for writing and reading data. For example, on the magnetic recording medium, data tracks are arranged concentrically. A magnetic head of a magnetic disk for writing and reading data is moved to a target side on the data track at high speed and is positioned to write bit information on the data track or to read out the already written bit information for writing and reading data.
On the other hand, on the magnetic recording medium, a positioning signal (servo signal) for detecting a relative position between the magnetic head and the data track is written in concentric fashion. The magnetic head performing writing and reading data detects own position at a given interval. For avoiding offset of the center of the servo signal from the center of the magnetic recording medium (or the center of a trace of the magnetic head), the servo signal is written on the medium using a dedicated apparatus called as servo writer after assembling the medium in the hard disk drive. Writing by the servo writer is performed by writing the servo signal to the magnetic recording medium using a servo signal writing head, for example.
On the other hand, the hard disk drive on development reaches a recording density of 20 Gbits/in2. The recording density is increasing at a speed of 60% or more per year. Associating with this, the density of the servo signal for enabling the magnetic head to detect own position is increased to inherently increase writing period by means of the servo writer. Increasing of the writing period by the servo writer should lower productivity of the hard disk drive to cause increasing of the cost.
In order to avoid increasing of the writing period of the servo signal, it has been recently proposed a transfer system for writing the servo signal in a lump by a magnetic transfer apparatus. Development of technology has been performed (for example, Japanese Patent Application Laid-Open No. 10-40544, Japanese Patent Application Laid-Open No. 11-25455). Writing of the servo signal by magnetic transfer, problem may be caused in transfer when scratch or contamination is present on the surface of the magnetic recording medium. Therefore, the magnetic recording medium has to be inspected by an optical type inspection apparatus.
In the magnetic transfer apparatus and the optical inspection apparatus, for transporting the magnetic recording medium or performing magnetic transfer and inspection for the magnetic recording medium, various movable portions are present. To the movable portion, a lubricant such as grease is applied. The grease can generate a gas due to friction upon operation of the movable portion or rising of temperature of the overall apparatus. Such gas may deposit on the surface of the magnetic recording medium to adversely affect for magnetic transfer or inspection.
The present invention has been worked out in view of the problem set forth above. An object of the present invention is to provide a selection method of a grease to be used in a movable portion of the magnetic transfer apparatus or the optical type inspection apparatus, and whereby to provide a magnetic transfer apparatus and an optical type inspection apparatus using such grease.
The first aspect of the present invention relates to a magnetic transfer apparatus for magnetically transferring a servo signal to a magnetic recording medium. The apparatus comprises:
a transfer stage for performing magnetic transfer;
an index portion performing positioning of a magnetic recording medium and supplying said magnetic recording medium to the transfer stage for a magnetic transfer operation;
a transporting portion for transporting the magnetic recording medium to the index portion;
wherein the magnetic transfer apparatus has a plurality of movable portions using a grease; and
wherein total amounts of a sulfur type gas generated from the plurality of the movable potions may be less than or equal to 0.5 ppb.
In the magnetic transfer apparatus of the present invention, total amount of the sulfur type gas generated may be preferably less than or equal to 0.35 ppb.
The second aspect of the present invention relates to an optical type inspection apparatus for optically inspecting scratch or foreign matter on a magnetic recording medium. The optical type inspection apparatus comprises:
an optical system for irradiating a light on the magnetic recording medium to inspect a surface of the magnetic recording medium;
an automatic focusing shaft for focusing the optical system;
a transporting portion for transporting the magnetic recording medium to the optical system;
wherein the optical type inspection apparatus has a plurality of movable portions using grease; and
wherein total amounts of a sulfur type gas generated from the plurality of the movable potions may be less than or equal to 0.5 ppb.
In the optical type inspection apparatus of the present invention, the total amount of sulfur type gas generated may be less than or equal to 0.35 ppb.
The third aspect of the present invention relates to a magnetic recording medium transferred a servo signal by the magnetic transfer apparatus described in the first aspect of the present invention, comprising at least a magnetic layer, a protective layer and a liquid lubricant layer on a substrate.
The fourth aspect of the present invention relates to a method for manufacturing a magnetic recording medium written a servo signal on a magnetic recording medium being performed by a magnetic transfer apparatus having a plurality of movable portions using a grease which may generate sulfur type gas in amount less than or equal to 0.5 ppb. The method comprises the steps of:
transporting the magnetic recording medium to an index portion for performing magnetic transfer operation;
performing magnetic transfer on a transfer stage for the magnetic recording medium transported to the index portion, thereby to obtain a magnetically transferred magnetic recording medium, and
collecting the magnetically transferred magnetic recording medium.
In the method for manufacturing the magnetic recording medium of the present invention, the magnetic transfer apparatus comprises:
a transfer stage for performing magnetic transfer;
an index portion performing positioning of a magnetic recording medium and supplying the magnetic recording medium to the transfer stage for magnetic transfer operation;
a transporting portion for transporting the magnetic recording medium to the index portion;
a plurality of movable portions using grease which may generate sulfur type gas in amount less than or equal to 0.5 ppb.
The method for manufacturing the magnetic recording medium of the present invention, the amount of the sulfur type gas generated may be less than or equal to 0.35 ppb.
The magnetic transfer apparatus according to the present invention may be the apparatus shown in FIG. 1, for example, but not limited to the particular construction.
The optical type inspection apparatus according to the present invention may be the apparatus shown in FIG. 2, for example, but not limited to the particular construction.
According to the present invention, by limiting concentration of gas which contains sulfur-containing compounds (hereinafter it refers sulfur type gas) generated from grease used in the magnetic transfer apparatus or the optical type inspection apparatus, the magnetic recording medium processed by such apparatus will not be damaged or corrosion even when it is left in high temperature and high humidity environment, and production of magnetic recording medium can be performed efficiently.